Humans have the ability to decode directional information from an incident sound with an acoustic transfer function. The head, the outer ears, and the body of a listener transform the spectral information from a sound in the space by means of what is called the Head-Related Transfer Function (HRTF), which allows us to perceive our acoustic environment based on the position, distance, etc. of sound sources and therefore to locate them.
HRTF filters consist of a pair of filters (left and right) that describe the filtering of a sound source at a given position by the body. It is commonly accepted that a set of about 200 positions is adequate for describing all of the directions in the space a person perceives. These HRTF filters essentially depend on the morphology of the ear (size, dimensions of the internal cavities, etc.) and other physical parameters of the person's body.
In the remainder of this document, the term “HRTF” represents the filters for all of the HRTF-type positions for a given subject.
Using the HRTFs in an audio application that are the closest possible to the listener's HRTF filters can achieve high-quality rendering. Several studies in the literature demonstrate the benefit of so-called individualized HRTFs (for example, see the Moller et al. article “Binaural technique: do we need individual recordings?” published in the Journal of the Audio Engineering Society: 44, 451-469), especially in terms of accuracy in location tests.
HRTF filters can be obtained by taking measurements with microphones in the listener's ear, or even by digital simulation. Despite the quality of these methods, they are still very tedious, very expensive, and inadaptable to consumer applications.
Moreover, a known method described in the document WO-01/54453, provides for selecting, within a database, the closest HRTFs to those of the user. However, unlike the invention, such a method that is effective in terms of statistics does not use the perceptual quality of the selection of HRTFs as a validation criterion and therefore does not select the best possible HRTFs.